A video camera, a digital still camera or the like each includes a camera lens, an image pickup means for converting the image light passing through the camera lens into an electric image signal, and a camera-signal processing means for processing the image signal. An output signal from the camera-signal processing means is output to the outside or is recorded in a recording medium.
In this connection, a so-called optical lens is employed for the camera lens. The image light passing through the camera lens from an object is separated into light of three primary colors of red (R), green (G), and blue (B) by, for example, a spectro-filter, and forms an image on a picture making plane of the image pickup means including a CCD, CMOS sensor and the like, and then converted into an electric image signal.
On the other hand, miniaturization of the video camera or digital still camera is rapidly pushed forward and miniaturization of the camera lens is also demanded. Accordingly, in order to miniaturize the camera lens, ones as before in which multiple lenses are combined and used is often replaced with a small one using a single lens or a few lenses. However, with such miniaturized camera lens, it will be difficult to sufficiently suppress the deterioration of picture quality caused in lens due to so-called chromatic aberration and the like.
Specifically, in the optical lens, a refractive index of the lens differs at each wavelength of red (R), green (G), and blue (B) separated by, for example, a spectro-filter, so that a phenomenon occurs in which a red (R) image is formed outside a green (G) image and a blue (B) image is formed inside the green (G) image, as shown in, for example, FIG. 4. Therefore, there is a problem in which even in the case where a monochrome image is taken, for example, a color blurring (color shift) appears at an edge of the image.
Thus, in order to suppress the deterioration of picture quality such as color blurring or resolution lowering due to such chromatic difference of magnification (also called lateral chromatic aberration), conventionally a large number of lenses were combined to perform correction inside the camera lens. However, in the above-described miniaturized camera lens, it becomes difficult to sufficiently suppress such deterioration of picture quality only inside the camera lens.
To cope with this difficulty, an apparatus disclosed in, for example, Japanese Published Patent Application No. H5-3568 is previously proposed as a means for suppressing the above-described deterioration of picture quality such as color blurring or resolution lowering due to the chromatic difference of magnification.
Specifically, the apparatus disclosed in the Patent Gazette is an apparatus in which image signals of each color of R, G, B derived from a CCD (image pickup device) are once converted into digital data and temporarily stored in each individual field memory, respectively. Further, based on a driving state of the camera lens such as a zoom focal length and a focal position, each picture stored in each field memory is enlarged or reduced by moving individually vectors of entire pixels in each field memory and then R, G, B are synthesized again for correcting the color shift occurring in the camera lens of a video camera.
Incidentally, when a picture is taken by a small-sized video camera or digital still camera, for example, held by hand, there is a risk that an image blurring due to so-called camera shake or the like may happen. Thus, for the purpose of removing the disadvantage such as the image blurring, a so-called camera shake correction device is installed in the small-sized video camera or digital still camera. FIG. 5 shows a block diagram of the video camera or digital still camera in which the camera shake correction device is installed.
In FIG. 5, image light from an object (not shown) passing through a camera lens 50 forms an image on the picture making plane of an image pickup means 51 including CCD, CMOS sensors and the like and is converted into an electric image signal including, for example, an intensity (Y) signal and two color-difference (Cb, Cr) signals. The image signal is supplied to a camera-signal processing circuit 52, where signal processing such as a so-called γ correction is made to form an ordinary image signal used for general-purpose video equipment. On the other hand, in order to detect the so-called camera shake, angular velocities due to the camera shake in Pitch and Yaw directions are detected using, for example, two gyro-sensors 53P and 53Y in this example. Moreover, for example, a zoom focal length of the camera lens 50 operated by a user is detected from the camera lens 50. Additionally, to detect the zoom focal length, an operational signal from a manual input means 54 operated by a user for example, can be employed.
The angular-velocity signals detected by the gyro-sensors 53P and 53Y are supplied to high-pass filters (HPF) 55P and 55Y, where DC components are removed; on the other hand, data on the above-described zoom focal length is supplied to a table 56 and necessary operational coefficients are found from those data; and the operational coefficients are supplied to multipliers 57P and 57Y, and are multiplied there by signals from the high-pass filters 55P and 55Y. Output signals from the multipliers 57P and 57Y are further supplied to integrators 58P and 58Y, respectively.
Therefore, information on angles of the camera lens 50 varied by the camera shake is derived from those integrators 58P and 58Y. The angular information on the camera shake is supplied to, for example, the image pickup means 51 through limiter circuits 59P and 59Y and a position at which the image signal is taken out from the image pickup means 51 is controlled. Specifically, for example, the image pickup means is provided with a picture making plane wider than a size of the original picture, and a necessary picture is taken out from the picture making plane so as to cancel out the fluctuation due to camera shake.
In this way, the so-called camera shake correction is performed in the small-sized video camera or digital still camera. Additionally, the following methods are practiced as a means for performing the camera shake correction other than controlling the position to take out the image signal from the camera means 51 as described above, in which all image signals captured by the image pickup means 51 are once stored in a memory 60 and then a position at which the image signal is read out from the memory 60 is controlled, or a partial lens position of the camera lens 50 is shifted for correction.
Furthermore, the information on angles of the camera lens 50 varied by the camera shake can also be taken out by the other means than that using the above-described gyro-sensors 53P and 53Y. For example, as shown in FIG. 6, by storing the image signal from the image pickup means 51 in a frame memory 61 and then comparing the image signals prior to and subsequent to the frame memory 61 with each other by a comparator circuit 62, it is possible to calculate the angular information on the camera shake from displacement of an image of the background and the like. In addition, the calculated angular information on camera shake can be utilized in all the above-described camera shake correction means.
However, it is proved that, when such camera shake correction is performed, if the compensation for the picture-quality deterioration such as color blurring or resolution lowering due to the chromatic difference of magnification is attempted, a sufficient correction cannot be made. Specifically, in the above-described device, when vectors of whole pixels in each field memory are moved individually, the center must correspond with an optical axis of the camera lens; however, if the camera shake correction is performed, the position of the optical axis is moved and it is difficult to correspond with the center.
For this reason, the compensation for picture-quality deterioration due to chromatic aberration, for example could not be performed simultaneously with the camera shake correction in the past. However, in conventional kinds of system having a small number of pixels, the picture-quality deterioration, for example, due to chromatic aberration is less noticeable, particularly when taking a picture requiring the camera shake correction. Lately, however, as the result that the increase in the number of pixels of a picture has been demanded, the influence of the picture-quality deterioration due to chromatic aberration or the like becomes conspicuous under every situation.
The present invention is made in view of the above and aims to solve the following problems. Conventionally, as the camera lens is miniaturized, the problem of picture-quality deterioration such as color blurring and resolution lowering is raised due to the chromatic difference of magnification, and it is difficult to sufficiently suppress the picture-quality deterioration only by the camera lens, and particularly when the compensation for such picture-quality deterioration is performed by enlarging or reducing a picture of each color, the problem is posed that the camera shake correction cannot be performed simultaneously therewith.